Method of manufacturing printed circuit boards

ABSTRACT

Methods and apparatus are provided to fabricate massive monolithic arrays of individually addressable light emitting diodes, assemble a plurality of such massive monolithic arrays of individually addressable light emitting diodes, control each individual light emitting diode, and to assemble the same in manner to achieve the accuracy and stability for a massive number of individually controlled light emitting diodes that can then be focused using projection optics on to a photoreceptive surface. In addition methods and apparatus are provided to move the imaging system thus described relative to the photoreceptive surface in two axes orthogonal to each other thus exposing the photoreceptive surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. ProvisionalApplication No. 61/178,146 filed May 14, 2009 entitled “Method To ObtainHigh Resolution Images On Photoreceptive Materials Using MassiveMonolithic Arrays Of Light Emitting Diodes”, the disclosure of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to a high speed imaging ofhigh resolution images on photoreceptive materials that may be coated onsubstrates using multiple massive individually addressable monolithicarrays of light emitting diodes (LEDs).

BACKGROUND INFORMATION

High resolution imaging on photoreceptive materials coated on to varioussubstrates is used in manufacturing processes such as manufacture ofsemiconductor devices, printed circuit boards and offset printing. Insuch manufacturing processes, the photoreceptive material may be exposedin a manner such as to create a desired image that, when additionalsteps are taken, produces a usable differentiation in the photoreceptivematerial in the exposed areas and unexposed areas. This difference maythen be used to advance the manufacturing process.

As one example, in offset printing, metal plates used may have a surfacewhich has been differentiated between areas that are hydrophobic andareas that are hydrophilic. The plates may then exposed to water. Thehydrophobic areas repel water, hydrophilic areas do not. When the platecomes in contact with ink, the ink is taken up by the areas where thereis no water. This pattern of ink may then be transferred indirectly topaper, thus generating a printed page.

Methods of creating images on these substrates have evolved over thedecades from projecting illuminated images through a lens onto asubstrate to the use of lasers and complex expensive mechanism to scanthe surface of the substrate. Common to all known imaging methods isthat the speed is constrained if the solution is to be practical interms of cost.

Embodiments of the present disclosure provide a method for imaging thatis high speed and cost effective.

Embodiments of the present disclosure provide methods and apparatus tochange or adapt the light source to the spectral sensitivity of thesubstrate.

Furthermore, embodiments of the present disclosure provide methods andapparatus for transporting an imaging mechanism over the substrate insuch a fashion as to provide the required precision, accuracy, andresolution for high speed resolution imaging.

Embodiments of this disclosure additionally provide methods andapparatus of controlling the intensity of the light emitting diodesthrough the using of voltage and current characteristics.

Embodiments of this disclosure also provide for the methods andapparatus to control each individual light in the monolithic lightemitting diode array at a speed consistent with the overall imagingrequirements.

SUMMARY OF THE DISCLOSURE

In accordance with embodiments of this disclosure, methods and apparatusare provided to fabricate massive monolithic arrays of individuallyaddressable light emitting diodes, assemble a plurality of such massivemonolithic arrays of individually addressable light emitting diodes,control each individual light emitting diode, and to assemble the samein manner to achieve the accuracy and stability required for a massivenumber of individually controlled light emitting diodes that can then befocused using projection optics on to a photoreceptive surface. Inaddition methods and apparatus are provided to move the imaging systemthus described relative to the photoreceptive surface in two axesorthogonal to each other thus exposing the photoreceptive surface.

The methods describe herein ensure the accuracy of the pixels producedby the methods and apparatus as well as the density that results in theimaging speed and the quality demanded by imaging systems for theapplications contemplated in embodiments of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention, together with further objects and advantages, maybest be understood by reference to the following description taken inconjunction with the accompanying drawings, in the several figures ofwhich like reference numerals identify like elements, and in which:

FIG. 1 is a pattern of the individual light emitting diode elements inan array, according to an exemplary embodiment.

FIG. 2 is a detail top layout of the arrangement of the light emittingdiodes forming a massive array, according to an exemplary embodiment.

FIG. 3 illustrates a plan of arrays and control electronics on a PrintedCircuit Board (PCB), according to an exemplary embodiment.

FIG. 4 shows layout of an array with bonding pads and the bonding padson a PCB, according to an exemplary embodiment.

FIG. 5 depicts a side view of the arrangement of an imaging assembly,according to an exemplary embodiment.

FIG. 6 depicts a plan view of the apparatus to support thephotoreceptive coated material and the transport components for the twoaxes, according to an exemplary embodiment.

FIG. 7 is a system block diagram depicting data and control informationmanagement, according to an exemplary embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This disclosure describes a method of applying the art of manufacturinglight emitting diodes to fabricate an array, preferably linear but notlimited to, in a pattern that is compatible with assembly of pluralityof such arrays into one massive array. Further, each array may be on adifferent substrate and process for achieving different levels ofefficiency and wavelength.

Manufacturing of light emitting diodes may include selecting materialsfor the band gap energy desired to achieve the target wavelength.Embodiments of the present disclosure are independent of the underlyingsemiconductor technology or methods used to manufacture the lightemitting diodes. The disclosure provided herein applies to any form ofmanufacturing of the light emitting diodes.

In a semiconductor manufacturing process a highly pure crystal wafer maybe exposed to specific impurities to build the different regions to formthe devices required. The pattern of these regions may be formed througha selective etching, deposition, and diffusion processes. The selectiveetching may take place through repeated coating of the crystal surfacewith a photo resistant material. This photo resistant material may thenbe exposed to a desired pattern carried on glass, termed a mask, usinglight of wavelength matching the sensitivity of the photo resistantmaterial (e.g., ultra violet).

According to one or more embodiments, the light emitting diodes may beplaced in a staggered manner such that alternate light emitting diodesare found in alternate columns. This may allow for gaps between adjacentlight emitting diode structures facilitating the semiconductorfabrication process. Gaps between adjacent light emitting diodes presenta challenge to use the array for high resolution imaging. As theadjacent light emitting diodes are now only adjacent in the orthogonalaxis and not the vertical axis, conventional methods of imaging mayresult in imaging difficulties. According to one or more embodiments ofthe present disclosure methods and apparatus may be used to makeadjacent light emitting diode structures appear adjacent, thus creatinga virtual massive linear array of lights.

FIG. 1 is a pattern of the individual light emitting diode elements inthe array showing the elements as square configuration of dimension m×nwhere m×n, where m is the desired width of an LED element and n is thedesired height of the LED element. According to some embodiments, theremay be two rows of elements, parallel to each other and separated by aknown distance that is, preferably, an integer multiple of the width mof the element, that is l×m where l is a positive non-zero integer and mis the dimension. Vertical separation may be equal to the height (n) ofthe element. The number of elements can vary according to size of waferand the application.

A set of masks may define the pattern of the devices created on thecrystal wafer. Thus the pattern of the light emitting diodes formingindividual elements of a massive array, each individually controllablemay be constructed. According to some embodiments, individual lightemitting diodes elements may be formed as squares of dimension m×n(where n=m) in two columns separated by a distance n in the verticaldirection (height) and a distance of l×m in the horizontal (width),where l is a non-zero positive integer. As illustrated in FIG. 1, LEDelements 102 a-102(e) may be separated by a vertical distance of n asshown in space 106 b. The vertical distance n may be equal to the heightof the LED elements 102 a-102(e) as shown in 106 a and 106 c. LEDelements 102 a-102(e) may be separated by a horizontal distance of l×mas shown in space 108. Horizontal distance m may be equal to the widthof LED elements 102 a-102(e) as shown in 104.

According to an exemplary embodiment, the dimensions may be m×n×20micrometers and l=4 and the number of elements in the array being 2048in two columns of 1024 each.

As illustrated in FIG. 1, LEDs 102 a and 102 b may be LEDs in a firstcolumn and LEDs 102 c, 102 d, and 102 e may be LEDs in a second column.The staggered arrangement of the two columns results in a space betweenany two light emitting diodes in one column (e.g., 106 b) that alignswith a light emitting diode in an adjacent column (106 a). Thisstaggered pattern may facilitate fabrication of the wafer. As discussedabove, this may present a challenge to imaging. According to someembodiments, the timing of the activation may depend on the row thelight emitting diode belongs to. The two rows may be activated in such amanner that the photoreceptors see the lights in one row. This isdiscussed in further detail in reference to FIG. 6 below.

FIG. 2 is a detail top layout of the arrangement of the light emittingdiodes forming a massive array. The total number of elements in eachcolumn may be determined by the yield curve of the manufacturingprocess. Each diode element 204 is shown to have a conductor 206 routedto a bonding pad or contact pad 202. Size of the bonding pads 202 may bedetermined by packaging technology.

Each individual light emitting diode element is connected to a bondingpad for wire bonding the element to the electronics assembly thusproviding a method to control each light emitting diode individually andseparately. The number of elements in the array may be limited by themanufacturing processes.

It should be clear to those conversant with the current art ofsemiconductor fabrication that a single wafer will produce devices thathave a very small spread in their characteristics. Thus a light emittingdiode array, being a part of a wafer, will have light emitting diodesthat emit light of equal intensity for equal current, and may have anidentical relationship between forward current and forward voltage.Light emitting diodes of the array may have a similar beam structurewithin the requirements of the applications envisioned in thisdisclosure. Due to the high purity of the semiconductor crystal waferand the consistency of the fabrication process, the light emitting diodearray may have the homogeneity required for graphic arts and other highquality high resolution high accuracy applications.

The arrangement described above may, when controlled appropriately andas described further below, generate a vertical line of pixels on theimage plane.

The positioning of each array in the assembly may require a highprecision of placements that may be achievable using standardsemiconductor mask alignment techniques.

Exemplary embodiments of these arrays contain a minimum of 256 LEDs andas many as the size of wafer will allow. The limitation of the wafer maybe determined by available crystal wafer size. According to someembodiments, these arrays may have two rows of 1024 LED elements each.

FIG. 3 illustrates a plan of arrays and control electronics on a PrintedCircuit Board (PCB) 302, according to an exemplary embodiment.

PCB 302 may carry the electronics, shown as a block diagram in FIG. 3.The electronics may receive data and control information from a remotesource (e.g., a computer connected via data connector 304). Exemplarycontrol information may include, amongst other information, lightintensity required, tables representing the light emitting diodes, andforward current to intensity characteristics of the light emittingdiodes. Power connector 306 may connect to electrical mains or otherelectrical power supply.

The data and control information may be received by one or more circuitsembedded in the PCB (e.g., Field Gate Programmable Array (FPGA) 308) viadata connector 304. Data received by FPGA 308 or other circuits may bepassed onto the shift registers in a first in first out basis and thento the driving electronics. For example, data may be received by FPGA308 and then passed to one or more Complex Programmable Logic Devices(CPLD) 310 a, 310 b, 310 c, and 310 d. Each of Complex ProgrammableLogic Devices (CPLD) 310 a, 310 b, 310 c, and 310 d may be responsiblefor a subset of LED elements (e.g., 512 LED elements for each CPLD).Control information may be used to control the light intensity in thelight emitting diodes of LED arrangement 314 through one or more methodsand/or components. Control information may also be used for setting theparameters for the timing and control electronics.

As the light emitting diodes within an array are formed simultaneouslyon one wafer, the light intensity to current relationship may be wellwithin the range of variations tolerated by the applications visualizedin this disclosure. Therefore to control the intensity of the lightemitting diodes within one monolithic array, according to someembodiments, a programmable voltage source may be used (e.g.,Programmable Voltage Source (PVS) 312). By changing the voltage appliedto the light emitting diodes using a programmable voltage source, thecurrent to diodes in an array may be changed and may thus change theintensity of the diode emissions. The drive electronics may containstorage for retaining the relationship of the current vs light intensityfor the array (e.g., non-volatile electronic storage such as processornon-volatile memory that maintains its contents regardless ofavailability of power). According to some embodiments, CPLDs 310 a, 310b, 310 c, and 310 d may store current to light intensity ratio data forthe one or more subsets of LED devices. For example, CPLD 310 a maystore and utilize current to light intensity data for LED elements 0-511of an array, CPLD 310 b may store and utilize current to light intensitydata for LED elements 512-1023 of an array, CPLD 310 c may store andutilize current to light intensity data for LED elements 1024-1535 of anarray, and CPLD 310 d may store and utilize current to light intensitydata for LED elements 1536-2048 of an array.

Intensity control as described above may be used to generate equalintensity in two or more light emitting diode arrays used to form adense array as described above.

Controlling the intensity of light in each individual light emittingdiode element may also be achieved using pulse width modulation of thecurrent through each LED element. This pulse width modulation may beachieved through the use of a table of data in the non volatile memorythat may be part of an embedded processor. The table of data may bebuilt during an initial calibration period where the light intensity maybe measured by an integrated power sensor (e.g., a photo-receptor)mounted in an apparatus.

To calibrate the elements of the array, each light emitting diodeelement may be turned on one at a time, and a reading from a powersensor may be obtained. The reading from the power sensor may then bestored in non-volatile memory. These values, one for each element, maythen be used to calculate the pulse width modulation period required tocorrect for the non-uniformity. This data may then be transferred to theappropriate control electronics so that when the light emitting diodesare switched on, they are switched off depending on this pulse widthdefinition transferred from the non-volatile memory to the controlelectronics (e.g., CPLDs). As different photo receptors have differentsensitivity to difference in intensity, one or both methods may be usedto achieve the desired uniformity of light intensity.

In other embodiments, to increase the efficiency of capture of lightfrom the light emitting diodes an array of micro lenses may be used.Another variation of one or more embodiments may use a higher degree ofdrivers in each Complex Programmable Logic Device (CPLD). One or moreembodiments may use specialized analog integrated circuits to drivespecific current control of each light emitting diode.

FIG. 4 illustrates a layout of an array with bonding pads and thebonding pads on the PCB. According to some embodiments, an imagingsystem as illustrated in FIG. 4 may be capable of imaging 2048 dots on aphotoreceptive surface. In other embodiments this number may beincreased by a multiple of k, where k may also increase or decrease. Asillustrated, k may equal one. As shown in FIG. 4, PCB 408 may containLEDs 204 a to 204 n. LEDs may be connected by connectors to bonding pads202 a, 202 b, 202 c, and 202 d. Bonding pads 202 a may be operativelyconnected to bonding pads 402 a. Bonding pads 202 h may be operativelyconnected to bonding pads 402 b. Bonding pads 202 c may be operativelyconnected to 402 c. Bonding pads 202 n may be operatively connected tobonding pads 402 d. Electronics 404 may connect to bonding pads 402 aand bonding pads 402 c. Electronics 406 may connect to bonding pads 402b and 402 n.

FIG. 5 depicts a side view of the arrangement of the imaging assembly502. The LED Array 514 may be mounted on a copper block 522 which mayalso carries the PCB containing the electronics 506 and 510. Thisassembly may then be enclosed in an aluminum or copper housing 504 witha projection lens 516 mounted at one end. The housing 504 may thensealed with inert gas replacing air. Outlets are provided on theexterior of the housing for the power, data and control signals (e.g.,outlets 512). Additional outlets can be provided if liquid cooling isrequired.

The massive individually addressable array of light emitting diodes 514may be mounted on copper base 522. This copper base 522 may then bemounted on a Peltier cooler 524 to provide thermal management of thedevice. The Peltier cooler 524 may then be controlled via a feed backloop consisting of electronics, temperature sensors and the Peltiercooler itself. Massive individually addressable array of light emittingdiodes 514 may project LED emissions via lense 516 onto imaging surface518. Various imaging ratios may be used. As depicted by optical axis 520in FIG. 5, according to an exemplary embodiment, a one-to-one ratio maybe used. Although a single complex lense is depicted, according to oneor more embodiments, a plurality of micro lenses may be provided (e.g.,an array of lenses and/or a lense per each LED element).

FIG. 6 depicts a plan view of the apparatus to support thephotoreceptive coated material and the transport components for the twoaxes. As illustrated in FIG. 6, imaging apparatus 600 may containsupports 612 a and 612 b which may support imaging assembly 602containing tense 604 and housing 606 over imaging surface 620. Accordingto some embodiments, imaging assembly 602 may contain one or morecomponents as discussed above in reference to FIG. 5 (e.g., massiveindividually addressable array of light emitting diodes 514). An arraycontained in imaging assembly 602 may be parallel to imaging surface 620and lense 604. Imaging assembly 602 may be mounted on rails 624 whichmay allow movement along an X axis. Encoder strip 610 may run across arange of movement of imaging assembly 602 on rails 624. Encoder strip610 may provide X axis positional indicators (e.g., magnetic, optical,etc.) to encoder read head 608. Imaging assembly 602 may moved alongrails 624 by one or more servo mechanical devices (e.g., a linearmotor). As further illustrated in FIG. 6, 614 a and 614 b may bebearings in linear rail 626 a. Linear rail 626 b may contain bearings614 c and 614 d. Linear rails 626 a and 626 b may allow motion along a Yaxis for imaging assembly 602. Encoder read head 616 may receive Y axispositional indicators from encoder strip 618.

The projection lens 604 may be selected to project the image with thedesired reduction to achieve the desired addressability and resolution.According to some embodiments, imaging surface 620 may be a part of avacuum system facilitating imaging by holding the imaging surface rigid.

The imaging assembly may then be mounted on a two axis motion system asshown in FIG. 6, with the photoreceptive material and its substrate on aflat table (e.g., imaging surface 620). In this embodiment, thephotoreceptive material may not move, the imaging system is moved in thetwo axes. The first motion may be across the photoreceptive material,referred to as the fast scan in the art; the second motion may beorthogonal to this first motion, referred to as the slow scan, and thenthe imaging system may reverse direction. Each fast scan may allow theimaging system to traverse completely over the photoreceptive materialand the imaging system may move orthogonally exactly the distancerequired for the last light emitting diode element of one scan to beadjacent to the first element of the second scan. This accuracy may bepossible by the linear motion system described above. The adjacency oflight emitting diodes between scans may be equal to the adjacency of thelight emitting diode elements within a scan.

The two axis motion system may control light emitting diodes by two axisservo system with very high resolution linear encoders and DC linearmotors on both axis. The linear motion systems are capable of theacceleration and high resolution as well as very high velocity controllight emitting diode. These attributes may provide a high qualityimaging systems for use in the applications envisioned for preferredembodiments.

During the motion of an imaging system across the photoreceptivematerial, the light emitting diodes may be activated through the datastored in the CPLDs. The timing of the activation may depend on the rowthe light emitting diode belongs to. During initial phase ofcommissioning the total system, software may be used to adjust therelationship of activating the two rows of light emitting diodes in eacharray. This software may use the encoder signal from the linear encoderof the linear motor to derive a signal that ensures that the two rowsare activated in such a manner that the photoreceptors see the lights inone row. This may be achieved by firing the two columns of LEDs in thearray at different times so that the firing of each takes place as theparticular column is over the same point on the imaging surface.

When the fast scan reaches its end of travel, the servo system mayreverse the direction of the motion while it advances the fast scanmechanism orthogonally (e.g., by a distance exactly equal to p*q*r wherep is the number of elements in the led array, q is the pitch of theprojected elements on the photoreceptor, and r is the number of ledarrays in an imaging assembly). According to one or more embodiments,the distance for a specific application, imaging on photopolymer platesfor newspaper application, could be 2048*20*4=163840 microns or 163.84mm.

The number of fast scans used may depend on the ration of the totallength of the photoreceptive materials and the orthogonal distancebetween subsequent fast scans.

FIG. 7 is a system block diagram depicting data and control informationmanagement, according to an exemplary embodiment. Data and controlinformation may be received at data transceiver processor 704 from anexternal source that may create the raster image to be imaged. This datamay be sent to FIFO shift registers 708 a, 708 b, 708 c, and 708 d thatmay be capable of buffering the data so that as one set of data is beingshifted out, the next can be shifted in. The control information may beused to set the voltage of the voltage source 706 and to set thetemperature and the variables for the timing and control system 702. Thetiming and control system 702 responds to the variable set as well asthe encoder signals coming from the XY motion systems. The drivers 710are activated as the imaging assembly is moving in relation to theencoder, which represents the physical location of the imaging assemblyand as such, the position of the LED array elements 712 in relation tothe photoreceptor on the imaging bed. Although voltage source 706 isdepicted as connected to drivers 710 d, it may be understood thatvoltage source 706 may be connected to all drivers 710 (e.g., drivers710 a, 710 b, 710 c, and 710 d).

It is further noted that the software described herein may be tangiblyembodied in one or more physical media, such as, but not limited to, acompact disc (CD), a digital versatile disc (DVD), a floppy disk, a harddrive, read only memory (ROM), random access memory (RAM), as well asother physical media capable of storing software, or combinationsthereof. Moreover, the figures illustrate various components separately.The functions described as being performed at various components may beperformed at other components, and the various components may becombined or separated. Other modifications also may be made.

In the preceding specification, various preferred embodiments have beendescribed with references to the accompanying drawings. It will,however, be evident that various modifications and changes may be madethereto, and additional embodiments may be implemented, withoutdeparting from the broader scope of invention as set forth in the claimsthat follow. The specification and drawings are accordingly to beregarded in an illustrative rather than restrictive sense.

I claim:
 1. A method of manufacturing a printed circuit boardcomprising: providing a photoreceptive material coating on a substrateof a printed circuit board; providing an array of multiple parallelcolumns of individually addressable light emitting diodes, the arraybeing fabricated from a wafer, the columns of light emitting diodesbeing arranged on the wafer in a staggered pattern such that a spacebetween any two light emitting diodes in any column aligns with at leastone light emitting diode in a different column, the staggered patternfacilitating fabrication of the wafer; determining an intensity of eachof the light emitting diodes; controlling light emitting diode emissionsusing the determined intensity of each of the light emitting diodes toform a high resolution image on the photoreceptive material to produce ausable differentiation in the photoreceptive material coating on saidprinted circuit board substrate between exposed areas and unexposedareas; and using said usable differentiation in the photoreceptivematerial coating in processing the printed circuit board substrate. 2.The method of claim 1, wherein controlling light emitting diodesemissions comprises: calculating a pulse width modulation period foreach of the light emitting diodes based on the measured intensity ofeach of the light emitting diodes, the calculated pulse width modulationperiod being configured to correct for non-uniformity of one or more ofthe light emitting diodes.
 3. The method of claim 2, further comprising:storing the calculated pulse width modulation period for each of thelight emitting diodes.
 4. A method of manufacturing a printed circuitboard comprising: providing a photoreceptive material coating on asubstrate of a printed circuit board; providing an array of individuallyaddressable light emitting diodes, the array being fabricated from awafer; determining an intensity of each of the light emitting diodes;controlling the intensity of light emitting diodes of the array usingthe determined intensity of each of the light emitting diodes using aprogrammable voltage source to regulate a voltage provided to the arrayto form a high resolution image on the photoreceptive material toproduce a usable differentiation in the photoreceptive material coatingon said printed circuit board substrate between exposed areas andunexposed areas; and using said usable differentiation in thephotoreceptive material coating in processing the printed circuit boardsubstrate, wherein regulation of the voltage provides control of acurrent to the light emitting diodes of the array and control of theintensity of the light emitting diode emissions.
 5. A method ofmanufacturing a printed circuit board, comprising: providing aphotoreceptive material; providing an array of individually addressablelight emitting diodes, the array being fabricated from a wafer;determining an intensity of each of the light emitting diodes;controlling light emitting diode emissions using the determinedintensity of each of the light emitting diodes to form a high resolutionimage on the photoreceptive material; regulating motion of an assemblyholding the array over an imaging surface of the photoreceptive materialin a X axis using a first encoder read head and a first encoder strip,the first encoder read head movement being synchronized with movement ofthe array along the X axis and the first encoder strip providing X axispositional indicators to the first encoder read head; and regulating themotion of the assembly holding the array over the imaging surface in a Yaxis using a second encoder read head and a second encoder strip, thesecond encoder read head movement being synchronized with movement ofthe array along the Y axis and the second encoder strip providing Y axispositional indicators to the second encoder read head, wherein the Xaxis positional indicators and the Y axis positional indicators providepositioning control of the array over the imaging surface to allow highresolution imaging.
 6. The method of claim 5, wherein the X axispositional indicators and the Y axis positional indicators are used incalculating timing of the emission of the individual light emittingdiodes of the array.
 7. The method of claim 1, wherein determining theintensity of each of the light emitting diodes comprises measuring theintensity of each of the light emitting diodes using an integrated powersensor.
 8. The method of claim 7, wherein the integrated power sensor isa photo-receptor.
 9. The method of claim 1, wherein the array iscomprised of first and second parallel columns of light emitting diodes.10. The method of claim 9, wherein the columns of light emitting diodesare arranged on the wafer such that a space between any two lightemitting diodes in the first column aligns with a light emitting diodein the second adjacent column.
 11. The method of claim 1, wherein timingand positioning of the emissions of the columns of light emitting diodescauses emissions of the columns of light emitting diodes to appear as asingle column to the photoreceptive material opposite the columns oflight emitting diodes.
 12. A method of manufacturing a printed circuitboard, comprising: providing a photoreceptive material coating on asubstrate of a printed circuit board; providing an array of individuallyaddressable light emitting diodes, the array being fabricated from awafer, the light emitting diodes being arranged on the wafer in astaggered pattern with respect to a direction of motion such that aspace between any two neighboring light emitting diodes aligns with atleast one light emitting diode; regulating motion of an assembly holdingthe array over an imaging surface of a photoreceptor along saiddirection of motion; timing an emission of the light emitting diodes tocause emissions from all of light emitting diodes to appear as a singlecolumn to the photoreceptor opposite the pattern of light emittingdiodes to produce a usable differentiation in the photoreceptivematerial coating on said printed circuit board substrate between exposedareas and unexposed areas; and using said usable differentiation in thephotoreceptive material coating in processing the printed circuit boardsubstrate to form a high resolution image on the photoreceptivematerial.